Reducing thermal shock high-temperature valve



Feb. 14, 1950 s, D, LAWSON 2,497,780

REDUCING THERMAL SHOCK HIGH-TEMPERATURE VALVE Filed April 27, 1945 l 2ll5 la 2o 24 A 2| la 47 E @www INVENTOR s D LAWSON 32 27 BY Y 6 F/aa. m"

ATTORNE Patented Feb. 14, 1950 REDUCING THERMAL SHOCK HIGH- TEMPERATUREVALVE Shelby D. Lawson, Bartlesville, Okla., assignor to PhillipsPetroleum Company, a corporation of Delaware Application April 27, 1945,Serial No. 590,668

l Claim.

1 1" This invention relates to valves. In one of its more specificaspects it relates to a means for the reduction of thermal shock invalves and fittings in high temperature service, particularly those oncyclic operation where the valves and fittings are subjected toalternate cooling and heating cycles.

It has been found that valves on processing units in the chemical andpetroleum industries which are operated on cyclic processes where thevalve is extremely hot (about 900 F. or higher) while in the openposition and cool during the period the valve is closed, develop cracksin the bodies of the valves. Hydrocarbon catalytic cracking units inwhich relatively long cycle periods are encountered are good examples ofservices in which this type of stress corrosion is found.

Metallurgical research has not to date developed a satisfactory alloy tostand up under such stress conditions and at the same time withstandchemical corrosion. Metals or alloys must be used which withstandchemical corrosion and in many cases such valloys have rather hightemperature coelcients of expansion, while some alloys having ybetterthermal properties, unfortunately, are not sufllciently chemicallyresistant to permit their use for economic and safety reasons.

Such failures, that is cracks in valve bodies, are apparently caused bya cool valve being subjected to an extremely hot stream of fluid whichheats the internal wall of the valve body to essentially fluidtemperature while the outside wall is still cool. It can be readily seenthat high compressional stresses will be setup in the internal sectionof the wall, the magnitude of these stresses varying vwith the wallthickness and the temperature differential across the wall section. Thecontinual application of these stresses causes cracks to appear. In acase which has come to applicants attention, cracks were discoveredafter a valve had been operated through only six cycles.

A partial solution to the problem resulted fromy v stand widetemperature variations.

Another object of my invention is to provide valves which will withstandsuch temperature changes as occasioned by olf-stream to on-stream inhigh temperature cyclic operations.

Stili another object of my invention is to provide a 'valve design andstructure for valves which experience extreme temperature changes.

Yet another object of my invention is to provide a valve structure whichwill withstand extreme cyclic temperature changes when alloys resistantto chemical corrosion are used in the oonstruction of the valve body.

Still other objects and advantages will be apparent to those skilled inthe art from a careful study of the following detailed description, inwhich Figure 1 of the drawing represents, diagrammatically, oneembodiment of my valve structure. Figures 2 and 3, also representvariable or equivalent valve structures embodying the same underlyingprinciple. Figure 4 is a plot showing the temperature relation of thevarious metal surfaces of a valve body embodying my invention.

In the figures of the drawing, numerals refer to the same or tocorresponding parts.

Referring particularly to Figure i, numeral Il refers to a. valvehousing or body having end flanges I2 for attachment to sections ofpipeor to other valves or pipe fittings. As illustrated in thisembodiment, this valve is a gate type valve. having a split gate Il,that is a wedge shape circular gate in two sections as indicated by i3dand I 3b. I'his gate is raised and loweredby a conventional hand wheelbonnet assembly, not shown, through a valve stem Il. The bonnet isattached to the valve body by means of the upper flange It. When thegate I3 is in its lowered 6r closed position sealed or fluid tightcontact is made with seat rings Il. These seat rings are standard partsor members of conventional type gatev valves and are ordinarily threadedand screwed into place or may be welded in place. both these methodsbeing in common practice.

When such a valve, that is, one composed of a body member, gate seats,and a gate, is in intermittent high temperature service. thermal strainsmay be excessive. When such a valve is at at- 3 mcspheric temperatureand upon opening a fluid of 90o-1100' F. begins to flow, it is obviousthat the valve body undergoes terrific strains. My experience has beenthat valves in such service fail by developing cracks. Such conditionsare magnied when valves are used in cyclic service. a8 in catalyticconversion operations where on stream" periods are high temperature andofi stream" or closed periods are at substantially atmospherictemperature. Frequent failures under such conditions are evidenced bydevelopment of cracks in the iianged ends of the body in the vicinity ofpositioning grooves I1. Obviously when cracks develop in any part of a.valve, especially if in high pressure service, the valve is unsafe andunt for further use. Housings or bodies of corrosion resistant alloysmay cost into the thousands of dollars depending on the size, forexample a 6 inch valve body only of corrosion resistant alloy isestimated to cost one thousand dollars, a 10 inch valve bodyone thousandtive hundred dollars. Thus, it is obvious that if my invention makespossible increased life of such valve bodies, and in these times ofmaterial shortages, such an advantage is of the utmost importance.

It might be mentioned that many other cracks develop in such valvesother than in the immediate vicinity of the positioning grooves I1.mentioned above.

One step in the protection of such valve bodies is to insulate thebodies so that during the oilstream" portion of a cycle the body willremain comparatively hot so that when the valve is opened to the ilow ofhigh temperature nuid, the temperature rise will not be so great. Thelire of such valve bodies has been materially lengthened when .insulatedas indicated in Figure 1.

As -a further protective means I have found that a liner inserted at aspaced distance from the valve body wall, increases valve life stilliurther. The object or reason for an increased life is due to theinsulating eiect oi' the air or gas space left between the liner andbody wall.

In the embodiment illustrated in Figure 1, the liner is composed of twoparts, a sleeve member Il and a conical member Ik' For illustrativepurposes I have assumed the liner of Figure 1 as a inch thick hollowcylindrical member being so designed and made as to slip into placeleaving a predetermined air space between the liner and the valve walls.To support the liner I8 I provide a series of "rings 20. These rings maybest be installed in the valve housing or body by welding, for example,prior to insertion of the liner il. As an alternative means of forminginsulating gas spaces 2|, the rings (2li) may be made by turning in alathe, and cutting away portions of the valve body excepting those to beleft as the rings. By whatever method the spacing means 29 is providedisfimmaterial, all that is necessary is to provide a mechanically strongand thermally suitable spacing means. The valve gate endof the liner Ilmay be beveled or cut at an angle determined by the wedge angle of thevalve gate. The liner may be welded in place lby any method suitable forthe purpose at hand taking into account materials of construction andother conditions understood by those skilled in such art.

The conical or tapcred liner members I9 are inserted on each side of thegate to act as protectors and provide insulating gas spaces ad- .iacentthe valve seat rings I5. These rings I5 may be threaded and screwed intoplace or preferably ma! be welded. The latter method makes certain thatthe seat rings remain rigidly attached to the valve body. Buch weldingmetal is indicated by the filled triangular spaces I! in Figure 1. Sincethe machined and smooth face of the seat member must not be covered norinterfered with in any manner, the conical member It is countersunk intothe valve body conduit with respect tothe valve seat, and this member(IS) is so constructed as to provide a gas space 2l similar to the otherinsulating spaces Il. The adjacent ends of the conical member il and theliner Il may be rigidly ilxed to the valve body by welding as indicatedby a ring of weld metal 24.

The outer end of the liner member Il is anged to permit welding to thellanges of the valve body,

the weld being indicated by weld metal 2l. In`

like manner the flanged end of the conical member Il is welded to thevalve seat meuiberA Il as indicated by reference numeral 26 in such aman ner that the weld metal does not interfere with the seating of valvegate. Thus such welding seals the annular cavities 28 between theconical member Is and the valve body. and the cavities 2i between thesleeve member Il and thc valve body and makes said annular spacessubstantially gas tight. While during the several mentioned weldingoperations gases will be sealed into these annular spaces II and Ilthere will be no free flowing oi iluids into or out of these spacesduring operation of the valve thus according more eillcient insulationmeans.

To assist in maintaining morenearly uniform temperature throughout thevalve body. I prefer to insulate the valve body with suitable insulainmaterial as indicated by reference numeral While in the abovedescription of the embodiment shown in Figure 1, I have disclosed theuse of a plain smooth cylindrical insulating sleeve (and means forsupporting same, this particular form of sleeve and support is notcritical since other forms are found to be useful and some evenadvantageous. Other embodiments of the sleeve and support members (I8of-Fig. 1) are illustrated in Figures 2 and 3.

In Figure 3 is shown a sumciently large portion of a valve body andinsulating member, in section, as to illustrate a second embodiment ofmy invention. This embodiment includes a seat member Ii and a conicalinsulating member II similar to those described hereinbefore in relationto Figure 1. In place of a smooth surfaced sleeve member (as I l inFigure l) a corrugated sleeve member l0 is used. This member is inlgeneral cylindrical in shape and has a llanged outer end 3| for weldingto the valve body ange. Both ends of this corrugated member I., theconical member I9 and seat member il are welded in place in a mannersimilar to that described for the assembly of Figure l. In place ofrings 2l of Figure 1 for forming the annular shaped gasl spaces ZI, inthe embodiment of Figure 3, the corrugations make corresponding annularinsulating spaces 32.

In Figure 2 is shown an embodiment of my invention incorporating thecorrugated sleeve member 3U of Figure 3 and the smooth, cylindricalsleeve member Il of Figure 1. The corrugated sleeve member Ila in thisembodiment is intended to be the equivalent of the rings 20 of Figure 1,that is, to serve as the support for the cylindrical sleeve member I8and at the same time to provide the annular insulating spaces II. Inthis Instance the corrugated sleeve member 36a need not be welded intoplace since the welding of sleeve I8 serves this purpose. Thus thesleeve member I8 has an exterior flange for attaching to the valve .bodyflange, and the corrugated sleeve 30a has none. Conical member I9 andthe valve seat ring I are similar to those of Figures 1 and 3. By usingsaid corrugated sleeve in this manner. double the number of annular gasspaces are provided as in the other embodiments with accordingly betterheat insulating properties.

To illustrate the advantage and utility of my method of controlling hightemperature valve temperatures, I have made standard calculationsshowing the temperature drop through the liner sleeve I6 of Figure 1,across the gas space 2| and through the valve body Il. For purposes ofcalculation Iassume the valve to be in a high temperature servicecarrying a fluid at 1100*I I". and. having an exterior valve bodytemperature oi 400 F. With an alloy, chemically non-corrosive liner 11,of an inch thick carrying a fluid at 1100 F. the temperature of theexterior surface ofA interface between the valve body and the insulationis taken at 400 F. for the above mentioned calculations. This value wasnot just arbitrarily assumed since it is in reality an operationaltemperature. It was found that when such a valve was open to 1100 F.fluid, the outer surface of the valve body after a while reached atemperature very near 1100 F. Then, when the valve was closed for anoff-stream portion of a cycle, thc valve slowly cooled and after fourhours the temperature of the valve body-insulation interface wasapproximately 400 l". At the end of the four hour off-stream period,upon opening the valve to 1100 F. fluid la thermal shock occurredl Theliner quickly became heated to the 1099 l". (as calculated), thenbecause of the inch air gap the interior of the valve body became onlyslowly heated to about 416, the exterior of the metal body remaining atthe 400 until the 418 F. temperature of ythe inner body is exceeded atwhich little from such a shock even when operating intermittently athigh temperature.

The corrugations of the liner illustrated in Figure 3 are shown astransverse with respect to the longitudinal axis of the valve body,they, however, may be disposed longitudinally. This latter arrangementmight be considered advantageous since itis obviously more conducive tostreamlined flow.

In like manner the corrugations of the supporting liner 30a of Figure 2may be arranged at right angles to the direction shown, or may bearranged helically or according to other design as desired, the severalrequirements of strength of construction and provision of air spacesbeing the important requirements. The rings 20 of Figure 1 may also bereplaced by metal strips arranged longitudinally with respect to fluidflow.

Materials of construction of such valves as herein disclosed may bechosen from among those commercially available. This type of valvemechanism was found advantageous especially when corrosion resistantmetal was used since such metal has a relatively high thermalcoetllcient of expansion, and my valve was found to offset at least someof the disadvantages of high expansion metals.

Having disclosed my invention, I claim:

A valve for use with high temperature nuids comprising a valve bodyforming two coaxial passagewalls spaced apart therein at their innerends, -the adjacent inner ends of the walls of said passages beingflared outwardly so as to form enlarged passage portions; imperforateflared liner members, smaller in diameter than said ared passageportions, spaced from the walls of said enlarged passage portions andrigidly amxed at their inner ends to the inner ends of said enlargedpassage wall por-tions so as to form gas time the exterior surfacetemperature increases, finally approaching the 1100". 'Ihus it isobvious that the maximum thermal shock occurs at a time when Ithetemperature difference between the inside oi' a valve and exterior isthe greatest. It is obvious, too, that when-a valve body is made of onethickness or layerof solid metal as is conventional in valveconstruction the thermal shock is severe. I have found that a valvecontaining e. liner as herein disclosed suil'ers comparatively tightseals therebetween; annular support members disposed along the length ofeach said passage wall and rigidly aillxed thereto so as to form gastight seals; and imperforate liner members extending from the outer endsof said flared liner members to the outer ends of said passages, beingaillxed at their inner ends to said flared liner members so as to formgas tight seais and secured in said annular support members so as toform a pluralityy of substantially gas tight chambers between saidpassage walls and said liners.

SHELBY D. LAWSON.

REFERENCES CITED The following references are of record in the ille ofthis patent:

UNITED STATES PATENTS Newton July 4, 1944

